linux-ext4 - Re: [PATCH v3 10/10] nf_conntrack: Use rcu

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Date:	Thu, 25 Jun 2009 16:33:44 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	jdb@...x.dk
CC:	Christoph Lameter <cl@...ux-foundation.org>, linux-mm@...ck.org,
	"David S. Miller" <davem@...emloft.net>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	dougthompson@...ssion.com, bluesmoke-devel@...ts.sourceforge.net,
	axboe@...nel.dk, christine.caulfield@...glemail.com,
	Trond.Myklebust@...app.com, linux-wireless@...r.kernel.org,
	johannes@...solutions.net, yoshfuji@...ux-ipv6.org,
	shemminger@...ux-foundation.org, linux-nfs@...r.kernel.org,
	bfields@...ldses.org, neilb@...e.de, linux-ext4@...r.kernel.org,
	tytso@....edu, adilger@....com, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH v3 10/10] nf_conntrack: Use rcu_barrier()

Jesper Dangaard Brouer wrote:
> RCU barriers, rcu_barrier(), is inserted two places.
> 
>  In nf_conntrack_expect.c nf_conntrack_expect_fini() before the
>  kmem_cache_destroy().  Firstly to make sure the callback to the
>  nf_ct_expect_free_rcu() code is still around.  Secondly because I'm
>  unsure about the consequence of having in flight
>  nf_ct_expect_free_rcu/kmem_cache_free() calls while doing a
>  kmem_cache_destroy() slab destroy.
> 
>  And in nf_conntrack_extend.c nf_ct_extend_unregister(), inorder to
>  wait for completion of callbacks to __nf_ct_ext_free_rcu(), which is
>  invoked by __nf_ct_ext_add().  It might be more efficient to call
>  rcu_barrier() in nf_conntrack_core.c nf_conntrack_cleanup_net(), but
>  thats make it more difficult to read the code (as the callback code
>  in located in nf_conntrack_extend.c).

Applied, thanks Jesper.
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